Septic systems, also known as subsurface sewage disposal systems, are extensively used to treat sewage from individual residences, businesses, schools, churches, military bases, or like structures, in areas not served by sewers. In the treatment of sewage by septic systems, solid and liquid waste from these structures is collected in a septic tank. Because of the different densities of solid and liquid waste, the solid and liquid components of the sewage will separate. The solid material is at least partially decomposed within the tank by the action of aerobic and anaerobic bacteria, resulting in a liquid effluent. The liquid effluent, which may contain suspended solids, is then conveyed out of the tank and distributed through a subterranean area which is typically referred to as a drain or leach field. The liquid effluent is passed to a series of buried temporary containment areas prior to discharge to the surrounding soil. The buried temporary containment areas or leaching trenches have traditionally been constructed of one or a combination of pipe and stone or sand trenches, or chambers within the leach field. Ultimately the effluent must pass through the buried containment area, after receiving pre-treatment, and then percolate through to the soil to receive final treatment before mixing with the underground water table.
Leach fields are typically divided into a number of portions (e.g., the aforementioned buried containment areas and leaching trenches) as dictated by the sewage treatment requirements of the structure serviced. Preferably, the effluent is distributed to the leaching trenches in an even and proportioned manner to minimize over-saturation of any localized area of the leach field. A plurality of underground tubes or pipes connects the septic tank to each of the portions of the leach field. Due in part to excavation needed to reach subsurface components as well as associated material and labor costs, the installation, repair and re-installation of the components of the septic system can be relatively expensive.
As can be appreciated, it is desirable to control installation costs and to extend the useful life of a septic system to minimize maintenance and repair costs. It is also desirable to achieve a high efficiency of treatment surfaces within each linear unit of leach field length to ultimately reduce or at least optimize the extent of the leach field area. It is further desirable to provide subsurface components that can be detected from above the surface to permit post installation location for inspection and/or future maintenance. It is additionally desirable to enable the sewage effluent to be evenly distributed throughout the leaching fields and for the treatment biomat to be able to evenly develop by receiving a balanced flow throughout a leaching system.
It is advantageous to provide a leaching system where the flow of sewage effluent can occur on treatment faces without passing through tortuous paths, corners, or distances that would impair the likelihood of even distribution to the treatment areas of the bottom and sidewalls of leach field components. In addition, it is desirable to isolate and protect the volume contained within a portion of a leaching system, or with a leaching system module, from sedimentation originating from the material used to cover the system. It is further advantageous to provide a means of distributing the liquid sewage effluent throughout the entire width and length of a leach field system regardless of failures that may develop within the system by bypassing the individual areas using bottom based balancing pipes.
The current state of the art includes the use of narrow containment structures configured such that the opposing faces are generally between two (2) inches and twelve (12) inches apart, generally parallel, and claimed to enhance aerobic activity. On some of the narrow systems it is either required or recommended to supplement the system with external air supply because of an inherent lack of oxygen.
Recent innovations in the art have been focused on the configuration of the parallel surfaces; which configuration also provides the mathematical formulation for calculating the maximum treatment surface area per linear foot of a pre-defined width of trench. Government regulators and engineers apply this formulation to define how consumers will utilize the systems. However, the pursuit of micro-level advances to achieve incrementally increasing degrees of treatment in the smallest footprint does not resolve macro-level considerations related to the total proportionate effluent distribution, balanced flow within the entire installed system, and the creation of balanced and even biomat formation.
The aerobic, anaerobic and facultative treatment processes vary with respect to a variety of parameters, such as for example: (i) the type and strength of effluent to be treated; (ii) the climate and climatic influence on the shallow subsurface; (iii) the conditions prevalent in the vertical strata of the region where leaching fields are installed and available having a permeability to provide final treatment and hydraulically convey the treated effluent away without saturation; and (iv) a soil that is free of standing water. Typically, a new leaching system is installed such that its bottom is a minimum distance from observed or historic groundwater, for example, in the area between the land surface and the water table known in the art as the vadose zone. As is known, the thickness of the vadose zone varies as the water table fluctuates in different seasons and during periods of drought.
Typically, there is sufficient oxygen in the shallow unsaturated subsoil environment to provide for aerobic conditions that are appropriate for leaching systems to function with full effect. There is little benefit in providing additional air or oxygen in an adequate air environment. The development of conditions resulting in a failure of a septic system is often the result of a combination of one or more of: a system having been installed where inadequate soil investigation had been performed; where a designer failed to address the basic principles of proper septic system design; the leaching system had been damaged and the effluent was not able to access the entire leaching system and localized over saturation was occurring; effluent was not able to be distributed though the leaching system either by external damage, installation error, or the inherent physical hydraulic overloading of the initial sections of a serial distribution where the initial sections had to be fully loaded to capacity before subsequent sections could receive flow. When saturated conditions are sustained, anaerobic conditions prevail.
The adequate supply of air within a new leaching system and the lack of need to provide supplemental air can be considered as follows. If a design cannot accommodate the inherent available air, the design should be reconsidered. This would be equally true of narrow systems. Such system design failure can be related to a garden pond environment where the pond water is removed by a pump and passed through a filter system. The filter system does not add oxygen to the water. The filter acts to promote biomat development on the filter media and then the water returns to the pond. The oxygen transfer is through the surface interface of the water and the air. The fish flourish. If air were to be added to the pond by aggressive waterfalls or aeration, the fish may still flourish but their condition would remain the same. The supplemental air would be superfluous to requirements and would simply be liberated to the environment. A correctly designed and installed pond and filter does not need additional air. However, if the pond were to have no filter, or the filter were failing, and the oxygen levels in the pond were being decreased by biological activity consuming the oxygen, the fish would benefit from the application of additional air.
A correctly designed and installed septic system exists where the air within the shallow soils allows adequate oxygen transfer for full biomat development and full functionality. If one area of a leaching field were to become saturated over prolonged periods, then aerobic activity would be depleted and localized anaerobic conditions would dominate, potentially progressing through the entire leaching system. Such a condition does not have a need to provide oxygen transfer which does not address the problem. Rather, the need is to establish a leaching system which promotes a system where the effluent is evenly distributed to ensure even biomat development. This even distribution is optimally accomplished with a combination of balancing flow pipes and the shape of the receiving leaching system treatment systems. As a result, any localized over-saturation leading to localized failure would be prevented by providing a balanced distribution of effluent throughout the entire leaching trench.
Typically, effluent, the flow that passes to the leaching field, is received from the septic tank as a gravity flow or as a pressure flow from a pump chamber. The effluent flows into a pipe or other conduit within the leaching trenches and thereby enters the leaching system, either chambers or stone trenches, or other horizontal system, in a progressive, serial distribution manner. The conditions of the flow, namely, the receiving volumetric flow rate which is a function of volume and velocity, will be modified by the conditions of the conduit. The conditions of the flow are dictated by many parameters including: the diameter of the conduit; the wetted perimeter of the flow; the depth of the flow; the roughness of the surface material of the conduit; and the temperature, viscosity, available capacity of openings in a pipe encountered during flow and the corresponding reduction in the quantity of flow by effluent leaving the pipe, and density of the effluent. For example, prior art stone-filled trenches include a conduit comprising a typical polyvinyl chloride (PVC) pipe having a diameter in the range of about three (3) inches to about four (4) inches. The effluent flow will pass along the length of the conduit and be contained until it encounters a point of discharge.
As shown in FIG. 1, a prior art conduit 1010 is a perforated pipe 1012 having a plurality of perforations 1014 oriented at the bottom quadrant of the pipe. An effluent flow 1016 is passed to the pipe 1012 at a volumetric flow rate, for example at a rate of five (5) gallons per minute (“gpm”). The effluent flow 1016 discharges via gravity feed through each of the perforations 1014 in a wall of the pipe 1012, where a perforation or hole may be any shape. Typically, a substantial portion 1018 of the effluent flow, for example four (4) gpm, will enter leaching media 1020 disposed about the pipe 1012 only at the initial perforations 1014 along a length of the pipe 1012. Substantially reduced portions 1022 and 1024 of the effluent flow 1016 will enter the leaching media 1020 downstream along the length of the pipe 1012 and at substantially reduced rates such as for example 0.75 gpm and 0.25 gpm, respectively. Similarly and as shown in FIG. 2, the typical prior art flow distribution pattern in a system where flow passes through a prior art conduit 1011 typically comprising a two (2) inch PVC pipe that discharges vertically into a leaching system, a single pipe 1026 having multiple bottom outlets 1028, typically of two (2) inches in diameter, may receive an effluent flow 1030 having a volumetric flow rate of five (5) gpm, wherein an entire volume of effluent flow 1032 may be discharged through a single, first-appearing bottom outlet 1028.
It can be readily understood that if the size of the first hole or perforation, or series of perforations, in a conduit or pipe is sufficiently large in proportion to the hydraulic characteristics of the effluent flow, then the effluent flow will enter the leaching system only at the initial perforation(s) of the pipe. The effluent flow will not pass over such initial perforations until the available capacity of the areas beneath, or being fed by, the perforations are at capacities such that overflow will occur. It can be clearly seen that there is an inherent dominance of the initial portion the state of the art leaching system to receive flow, and the overflow will generally only occur when the first portion is full. Accordingly, the entire leaching system is not being utilized in an even and distributed manner. Rather, the middle and end of the system will only be utilized when the initial areas are fully saturated or over time, when the prolonged saturation of the initial areas has caused anaerobic treatment and potentially system failure, and are no longer functioning or able to receive any significant effluent thereby forcing the distribution to downstream areas of the leaching field.
An example of this type of flow can be observed in a roadway system of catch basins installed in a gutter line when a fire hydrant is being serviced and a flow of water exemplifying a flow of effluent is being discharged into the gutter. The initial flow passes along the gutter and all of it enters the first catch basin. Even if more flow were to be released from the hydrant, the flow would still be captured by the first catch basin. If the flow were to be further increased so that the inlet to the first catch basin was overwhelmed, then the flow would pass into the first catch basin and the extra water would then bypass the first catch basin and flow to the next catch basin down gradient. Over time, and if the first catch basin were to become blocked, as would be the case in a fully saturated leaching trench, a very small quantity would go into the first catch basin and the vast majority of the flow would bypass it and enter the next catch basin. This may still leave the third, fourth and subsequent catch basins completely unutilized.
Accordingly, the inventor has determined that what is needed is a leaching system that incorporates appropriate hydraulic control having a means to force flow to all points of a system and to allow a sufficient rate of flow wherein there would be both entry into the initial perforations and bypass to the subsequent perforations, allowing equal and balanced utilization, until at full design utilization, substantially all of the available capacity of the area beneath, or being fed by, the perforations is at an equal and shared capacity. It is desired that this flow condition occur substantially along the entire length of the leaching system.
As applied to the series of catch basins handling an overwhelming flow as described above, the desired solution would incorporate establishing appropriate hydraulics having a sufficient rate of flow wherein there would be both entry into the first catch basin and bypass to the subsequent catch basins. For example, the flow from the hydrant should be passed along the gutter line in a level and horizontal pipe installed in the length of the gutter line such that the volume of water would be distributed evenly along the length of the gutter line. The pipe would have an outlet positioned on its top at each catch basin. Such a pipe configuration would permit a proportionate flow out of the pipe and to each catch basin wherein no single catch basin would be forced to receive a dominant proportion of the flow and all flow would be proportionate at the same time.
The prior art utilizes a top distribution pipe that receives the flow from the septic tank and distributes the effluent to the leach field through a series of distribution outlets into the top of the leaching areas. The prior art leaching systems vary in depth from about 3 inches to about 48 inches and have shapes comprising a fabric wrapped around a plastic core configured in a serpentine shape, stone filled “u” shapes with the legs originating from the distribution pipe, and cardboard divided stone areas with the leaching areas projecting from the central axis. Other configurations exist, but they are all consistent in that they are dependent upon top feeding. If the top pipe is broken during installation, installed in such a manner wherein the distribution pipe is not level such that a low distribution area is formed, or the main distribution pipe is damaged or impaired during installation, backfilling, or by the use of the land by equipment of the land owner, such as trucks, landscaping equipment or the like, the flow will not occur as designed and hydraulic overloading will occur.
Once the sewage effluent has been discharged into the leaching field in a disproportionate manner, or even if the sewage effluent has been discharged in a proportionate and balanced manner, an additional enhancement or a coupled enhancement is needed to maintain the even and balanced distribution through the entire leaching field which would compensate for the issues related to the errors and inadequacies of top distributed leaching systems. The inventor has determined that what is needed is a hydraulic connectivity that serves to bypass surface distribution pipe failures that can occur from collapse during installation by being compressed by large construction equipment, or by having been installed in such a manner that low points or high points impaired the flow of effluent along the pipe and the effluent entered the system at a concentrated location. In a current condition, this would cause overloading of this individual portion of the leaching field resulting in premature failure. What is needed is a distribution system wherein the effluent would simply be conveyed across and along the full width and length of the leaching field in an equal and balanced manner. What also is needed is a method wherein the aforementioned prior art can be modified or retrofitted to incorporate such hydraulic connectivity to ensure full width and length distribution. The modified or retrofit connectivity should be capable of being installed in “u” shapes, serpentine shapes, “L” shapes, or any other shape where a leaching system has a bottom with a width and a length.
Accordingly, what is needed is a system that provides a reliable quantity of effluent in proportion to the available treatment areas that are being utilized over the life of the system with a minimum of inspection and maintenance of the system. Preferably, the system is non-mechanical and self-adjusting.